package com.lagou.sqlSession;

import com.lagou.pojo.Configuration;
import com.lagou.pojo.MappedStatement;

import java.lang.reflect.*;
import java.util.List;
import java.util.Objects;

public class DefaultSqlSession implements SqlSession {

    private Configuration configuration;

    public DefaultSqlSession(Configuration configuration) {
        this.configuration = configuration;
    }

    @Override
    public <E> List<E> selectList(String statementid, Object... params) throws Exception {

        //将要去完成对simpleExecutor里的query方法的调用
        simpleExecutor simpleExecutor = new simpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementid);
        List<Object> list = simpleExecutor.query(configuration, mappedStatement, params);

        return (List<E>) list;
    }

    @Override
    public <T> T selectOne(String statementid, Object... params) throws Exception {
        List<Object> objects = selectList(statementid, params);
        if (objects.size() == 1) {
            return (T) objects.get(0);
        } else {
            throw new RuntimeException("查询结果为空或者返回结果过多");
        }


    }

    /**
     * 新增数据
     *
     * @param statementId
     * @param params
     * @return
     * @throws Exception
     */
    @Override
    public boolean insert(String statementId, Object params) throws Exception {
        if (Objects.isNull(params)) {
            return false;
        }
        Executor executor = new simpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        return executor.insert(configuration, mappedStatement, params);
    }

    /**
     * 修改数据
     *
     * @param statementId
     * @param params
     * @return
     * @throws Exception
     */
    @Override
    public boolean update(String statementId, Object params) throws Exception {
        if (Objects.isNull(params)) {
            return false;
        }
        Executor executor = new simpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        return executor.update(configuration, mappedStatement, params);
    }

    /**
     * 删除数据
     *
     * @param statementId
     * @param id
     * @return
     * @throws Exception
     */
    @Override
    public boolean delete(String statementId, Object id) throws Exception {
        if (Objects.isNull(id)) {
            return false;
        }
        Executor executor = new simpleExecutor();
        MappedStatement mappedStatement = configuration.getMappedStatementMap().get(statementId);
        return executor.delete(configuration, mappedStatement, id);
    }


    @Override
    public <T> T getMapper(Class<?> mapperClass) {
        // 使用JDK动态代理来为Dao接口生成代理对象，并返回

        Object proxyInstance = Proxy.newProxyInstance(DefaultSqlSession.class.getClassLoader(), new Class[]{mapperClass}, new InvocationHandler() {
            @Override
            public Object invoke(Object proxy, Method method, Object[] args) throws Throwable {
                // 底层都还是去执行JDBC代码 //根据不同情况，来调用selctList或者selectOne
                // 准备参数 1：statmentid :sql语句的唯一标识：namespace.id= 接口全限定名.方法名
                // 方法名：findAll
                String methodName = method.getName();
                String className = method.getDeclaringClass().getName();

                String statementId = className + "." + methodName;


                methodName = methodName.startsWith("find") ? "select" : methodName;

                switch (methodName) {
                    case "select":
                        // 获取方法返回值类型
                        Type returnType = method.getGenericReturnType();
                        if (returnType instanceof ParameterizedType) {
                            // 如果方法类型有泛型，则判断是返回List
                            return selectList(statementId, args);
                        }
                        return selectOne(statementId, args);
                    case "insert":
                        return insert(statementId, args);
                    case "update":
                        return update(statementId, args);
                    case "delete":
                        return delete(statementId, args);
                    default:
                        break;
                }

                // 准备参数2：params:args
                // 获取被调用方法的返回值类型
                Type genericReturnType = method.getGenericReturnType();
                // 判断是否进行了 泛型类型参数化
                if (genericReturnType instanceof ParameterizedType) {
                    List<Object> objects = selectList(statementId, args);

                    return objects;
                }

                return selectOne(statementId, args);

            }
        });

        return (T) proxyInstance;
    }


}
